Re: [PATCH 2/3] configure.ac: check for clock_gettime and CLOCK_MONOTONIC

[Eric Sunshine <sunshine@sunshineco.com>]

On Wed, Jan 7, 2015 at 5:31 PM, Reuben Hawkins <reubenhwk@gmail.com> wrote:
> On Wed, Jan 7, 2015 at 1:37 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
>> On Wed, Jan 7, 2015 at 3:23 PM, Reuben Hawkins <reubenhwk@gmail.com> wrote:
>>> +GIT_CHECK_FUNC(clock_gettime,
>>> +[HAVE_CLOCK_GETTIME=YesPlease],
>>> +[HAVE_CLOCK_GETTIME=])
>>> +GIT_CONF_SUBST([HAVE_CLOCK_GETTIME])
>>
>> You could simplify the above four lines to this one-liner:
>>
>>     GIT_CHECK_FUNC(clock_gettime,
>>         GIT_CONF_SUBST([HAVE_CLOCK_GETTIME], [YesPlease]))
>>
>>> +AC_MSG_CHECKING([for CLOCK_MONOTONIC])
>>> +AC_COMPILE_IFELSE([CLOCK_MONOTONIC_SRC],
>>> +       [AC_MSG_RESULT([yes])
>>> +       HAVE_CLOCK_MONOTONIC=YesPlease],
>>> +       [AC_MSG_RESULT([no])
>>> +       HAVE_CLOCK_MONOTONIC=])
>>> +GIT_CONF_SUBST([HAVE_CLOCK_MONOTONIC])
>>
>> Ditto regarding simplification:
>>
>>     AC_MSG_CHECKING([for CLOCK_MONOTONIC])
>>     AC_COMPILE_IFELSE([CLOCK_MONOTONIC_SRC],
>>         [AC_MSG_RESULT([yes])
>>         GIT_CONF_SUBST([HAVE_CLOCK_MONOTONIC], [YesPlease])],
>>         [AC_MSG_RESULT([no])])
>
> I *think* there's an issue with this simplification as used right
> here.  In the 'no' case, HAVE_CLOCK_MONOTONIC *must* be undefined by
> setting it equal to nothing
>
> HAVE_CLOCK_MONOTONIC=
>
> So that the setting in config.mak.uname 'HAVE_CLOCK_MONOTINIC =
> YesPlease' will be overridden.
>
> So this one needs to stay as is.

Yes, you're right. That means that the HAVE_CLOCK_GETTIME
simplification also suffers the same shortcoming. So, neither
simplification is appropriate in this instance. Sorry for the noise.